Before paying the collection, negotiate a PFD. Paying a collection will never improve your FICO score. Per FICO, it doesn't matter if the balance is $0, or $10,000, the damage is equal. I personally would send a DV prior to the PFD.

If T-Mobile was reporting as a CO and was removed, then it could possibly help.

Re: Advice on bumping credit score

Follow llec advice and work on getting the collection taken care of while your doing that your scores will probably increase anyway if you have not applied for any new credit and any INQ's you have are aging.

Good luck and welcome to the forum

Before you app think...Have you done your research of the CC?Does it fit your spending?Do you have a plan for the bonus w/o going into debt?Can you afford the AF?Do you know the cards benefits? Is it worth the HP?

IMPORTANT INFORMATION: All FICO® Score products made available on myFICO.com include a FICO® Score 8, along with additional FICO® Score versions. Your lender or insurer may use a different FICO® Score than the versions you receive from myFICO, or another type of credit score altogether. Learn more

FICO, myFICO, Score Watch, The score lenders use, and The Score That Matters are trademarks or registered trademarks of Fair Isaac Corporation.
Equifax Credit Report is a trademark of Equifax, Inc. and its affiliated companies.
Many factors affect your FICO Scores and the interest rates you may receive. Fair Isaac is not a credit repair organization as defined under federal or state law, including the Credit Repair Organizations Act. Fair Isaac does not provide "credit repair" services or advice or assistance regarding "rebuilding" or "improving" your credit record, credit history or credit rating.
FTC's website on credit.

IMPORTANT INFORMATION: All FICO® Score products made available on myFICO.com include a FICO® Score 8, along with additional FICO® Score versions. Your lender or insurer may use a different FICO® Score than the versions you receive from myFICO, or another type of credit score altogether. Learn more

FICO, myFICO, Score Watch, The score lenders use, and The Score That Matters are trademarks or registered trademarks of Fair Isaac Corporation. Equifax Credit Report is a trademark of Equifax, Inc. and its affiliated companies. Many factors affect your FICO Score and the interest rates you may receive. Fair Isaac is not a credit repair organization as defined under federal or state law, including the Credit Repair Organizations Act. Fair Isaac does not provide "credit repair" services or advice or assistance regarding "rebuilding" or "improving" your credit record, credit history or credit rating. FTC's website on credit.